Go to the Herd website. I do believe they have a "dealer locator". If not, they definately have a "contact us". I'm sure they'll be able to assist you in finding SOMEONE who'll sell you a seeder. I've got 2 of them (1 big, 1 small...don't recall model #s) They are fine products, well worth the effort in finding a local dealer.
Personally, I'd start with a phone call to all your area dealers, especially any with a good AG equipment base. Herd is a VERY big seller. I'd find it hard to believe SOMEONE won't be able to get you one.